Updated Animation to optionally use SIMD

SIMD structures can now be used to calculate bone transforms.
Updated Animation to optionally use SIMD

SIMD structures can now be used to calculate bone transforms.
Rebased, renamed SIMD views to match John's naming convention
Merged
Set up UI for swapping between SIMD and non-SIMD code paths.
Merge pull request #90 from toji/skinning

SIMD Posing + UI
Fix asset_pack demo

Switch to walk7 animation.

Signed-off-by: John McCutchan <john@johnmccutchan.com>
Fix update call.

Signed-off-by: John McCutchan <john@johnmccutchan.com>
UI for changing number of instances

With better layout for N instances
Stubbing in skinning shader

Converted all verts to have 4 weights
Almost have GPU skinning working. Need to stop software skinning when GPU skinning is enabled
GPU Skinning is fully functional
re-added update
Merge pull request #91 from toji/skinning

GPU Skinning